Stack Memory vs Heap Memory


Java runtime uses two types of memory: Stack and Heap. Stack stores value of local primitive variables, local object references (not object values) and method parameters. Static variables, static methods, instance objects and instance methods are stored in the heap as they have to live longer than the stack.

Stack memoryHeap memory
Stack memory has stack of data. That is, data arranged one on top of anotherHeap memory has data arranged just like heap of dust. That is, arranged without any order
Stack data can be accessed in Last In First Out(LIFO) order. LIFO means what is stored last on the stack can be accessed or removed first from the stackHeap memory is allocated at any time and deallocated in any order
It is simple to track data located in a stackIt is difficult to track data located in a heap
Stack memory is limited in sizeHeap memory has relatively more memory than in a stack
Accessing stack memory is fasterAccessing heap memory is relatively slower
Stack is a data structure implemented using simple arrays or a listHeap is a specialized tree structure implemented using priority queue
Stack memory is allocated separately per thread in RAMHeap memory is allocated and accessible to all processes in RAM
When a thread starts, memory allocation is done while execution progresses. When a thread exits, stack memory allocated for a particular thread becomes freeWhen a process starts, heap memory is allocated. Deallocation happens for unused memory as Garbage collection happens. Complete deallocation can be done only when the process stops
Stack memory stores local variablesHeap memory stores objects in Java
Stack memory size can be configured using "-Xss <stack size >" option for the java runtimeHeap memory size can be configured using "-Xms <Initial size> -Xmx <Maximum size> " option
Stack memory is used for data which needs to be removed when the method exitsHeap is used for Objects which may be needed outside the methods in which memory is allocated first



Stack Memory vs Heap Memory


Java runtime uses two types of memory: Stack and Heap. Stack stores value of local primitive variables, local object references (not object values) and method parameters. Static variables, static methods, instance objects and instance methods are stored in the heap as they have to live longer than the stack.

Stack memoryHeap memory
Stack memory has stack of data. That is, data arranged one on top of anotherHeap memory has data arranged just like heap of dust. That is, arranged without any order
Stack data can be accessed in Last In First Out(LIFO) order. LIFO means what is stored last on the stack can be accessed or removed first from the stackHeap memory is allocated at any time and deallocated in any order
It is simple to track data located in a stackIt is difficult to track data located in a heap
Stack memory is limited in sizeHeap memory has relatively more memory than in a stack
Accessing stack memory is fasterAccessing heap memory is relatively slower
Stack is a data structure implemented using simple arrays or a listHeap is a specialized tree structure implemented using priority queue
Stack memory is allocated separately per thread in RAMHeap memory is allocated and accessible to all processes in RAM
When a thread starts, memory allocation is done while execution progresses. When a thread exits, stack memory allocated for a particular thread becomes freeWhen a process starts, heap memory is allocated. Deallocation happens for unused memory as Garbage collection happens. Complete deallocation can be done only when the process stops
Stack memory stores local variablesHeap memory stores objects in Java
Stack memory size can be configured using "-Xss <stack size >" option for the java runtimeHeap memory size can be configured using "-Xms <Initial size> -Xmx <Maximum size> " option
Stack memory is used for data which needs to be removed when the method exitsHeap is used for Objects which may be needed outside the methods in which memory is allocated first



Learn about Stack Data Structure

Learn about Heap Data Structure

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Learn Djikstra's Algorithm